1、HttpComponents項目的介紹
先介紹一下一個開源項目， 這個項目就是Apache開源組織中的HttpComponents，主要是提供對http服務器的訪問功能，目前已經是一個單獨的項目，可見http服務器的訪問絕非易事。
在某些時候可能需要通過程序來訪問這別人的網頁程序，比如從別人的網頁中“偷”一些數據。如果對方僅僅是一個很簡單的頁面，那我們的程序會很簡單，。但是考慮到一些服務授權的問 題，很多公司提供的頁面往往並不是可以通過一個簡單的URL就可以訪問的，而必須經過注冊然后登錄后方可使用提供服務的頁面，這個時候就涉及到 COOKIE問題的處理。我們知道目前流行的動態網頁技術例如ASP、JSP無不是通過COOKIE來處理會話信息的。為了使我們的程序能使用別人所提供的服務頁面，就要求程序首先登錄后再訪問服務頁面！再比如通過HTTP來上傳文件呢？
HttpComponents項目就是專門設計來簡化HTTP客戶端與服務器進行各種通訊編程。通過它可以讓原來很頭疼的事情現在輕松的解決，例如你不再管是HTTP或者HTTPS的通訊方式，告訴它你想使用HTTPS方式，剩下的事情交給 httpclient替你完成。
網址：http://www.apache.org/ 主頁下面的Projects 可以找到HttpComponents項目，下載到相應的jar包，以及源代碼跟示例程序。
2、httpcomponents 4.5.2 簡單使用
HttpComponents 也就是以前的httpclient項目，可以用來提供高效的、最新的、功能豐富的支持 HTTP 協議的客戶端/服務器編程工具包，並且它支持 HTTP 協議最新的版本和建議。不過現在的 HttpComponents 包含多個子項目，有：
HttpComponents Core
HttpComponents Client
HttpComponents AsyncClient
Commons HttpClient
以下列出的是 HttpClient 提供的主要的功能，要知道更多詳細的功能可以參見 HttpClient 的主頁。
實現了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
支持自動轉向
支持 HTTPS 協議
支持代理服務器等
支持Cookie
之前用的HttpClient的方法都失效了，比如 httpclinet =new DefaultHttpClient(); 不知道為啥包里80%的類都失效了，總是覺得創建一個httpclient實例會比較麻煩，記不住。所以整理了一下新的方式簡單使用。
簡單使用
導入jar包
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
get請求獲取響應
CloseableHttpClient httpClient= HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://www.baidu.com");
CloseableHttpResponse response = httpClient.execute(httpget);
HttpEntity httpEntity= response.getEntity();
String strResult= EntityUtils.toString(httpEntity);
post請求獲取響應
HttpPost httpost = new HttpPost("https://www.baidu.com");
List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("IDToken1", "username"));
nvps.add(new BasicNameValuePair("IDToken2", "password"));
httpost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));
HttpClient提供URIBuilder工具類來簡化URIs的創建和修改過程。
URI uri = new URIBuilder()
.setScheme("http")
.setHost("www.google.com")
.setPath("/search")
.setParameter("q", "httpclient")
.setParameter("btnG", "Google Search")
.setParameter("aq", "f")
.setParameter("oq", "")
.build();
HttpGet httpget = new HttpGet(uri);
System.out.println(httpget.getURI())
模擬瀏覽器請求
httpget.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0");
3、HttpComponents之httpclient基本使用方法 - httpclient的版本是4.3
A、第一種方式
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class HttpClient2 {
public static void main(String args[]) throws IOException {
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("account", ""));
formparams.add(new BasicNameValuePair("password", ""));
HttpEntity reqEntity = new UrlEncodedFormEntity(formparams, "utf-8");
RequestConfig requestConfig = RequestConfig.custom()
.setSocketTimeout(5000)
.setConnectTimeout(5000)
.setConnectionRequestTimeout(5000)
.build();
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost("http://cnivi.com.cn/login");
post.setEntity(reqEntity);
post.setConfig(requestConfig);
HttpResponse response = client.execute(post);
if (response.getStatusLine().getStatusCode() == 200) {
HttpEntity resEntity = response.getEntity();
String message = EntityUtils.toString(resEntity, "utf-8");
System.out.println(message);
} else {
System.out.println("請求失敗");
}
}
}
B、第二種方式，這種方式是用了一個http的連接池，同時使用httpbuilder構造合適的http方法。
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.client.methods.RequestBuilder;
import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import java.io.IOException;
import java.util.*;
public class HttpClientUtils {
private static PoolingHttpClientConnectionManager connectionManager = null;
private static HttpClientBuilder httpBulder = null;
private static RequestConfig requestConfig = null;
private static int MAXCONNECTION = 10;
private static int DEFAULTMAXCONNECTION = 5;
private static String IP = "cnivi.com.cn";
private static int PORT = 80;
static {
//設置http的狀態參數
requestConfig = RequestConfig.custom()
.setSocketTimeout(5000)
.setConnectTimeout(5000)
.setConnectionRequestTimeout(5000)
.build();
HttpHost target = new HttpHost(IP, PORT);
connectionManager = new PoolingHttpClientConnectionManager();
connectionManager.setMaxTotal(MAXCONNECTION);
connectionManager.setDefaultMaxPerRoute(DEFAULTMAXCONNECTION);
connectionManager.setMaxPerRoute(new HttpRoute(target), 20);
httpBulder = HttpClients.custom();
httpBulder.setConnectionManager(connectionManager);
}
public static CloseableHttpClient getConnection() {
CloseableHttpClient httpClient = httpBulder.build();
httpClient = httpBulder.build();
return httpClient;
}
public static HttpUriRequest getRequestMethod(Map<String, String> map, String url, String method) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
Set<Map.Entry<String, String>> entrySet = map.entrySet();
for (Map.Entry<String, String> e : entrySet) {
String name = e.getKey();
String value = e.getValue();
NameValuePair pair = new BasicNameValuePair(name, value);
params.add(pair);
}
HttpUriRequest reqMethod = null;
if ("post".equals(method)) {
reqMethod = RequestBuilder.post().setUri(url)
.addParameters(params.toArray(new BasicNameValuePair[params.size()]))
.setConfig(requestConfig).build();
} else if ("get".equals(method)) {
reqMethod = RequestBuilder.get().setUri(url)
.addParameters(params.toArray(new BasicNameValuePair[params.size()]))
.setConfig(requestConfig).build();
}
return reqMethod;
}
public static void main(String args[]) throws IOException {
Map<String, String> map = new HashMap<String, String>();
map.put("account", "");
map.put("password", "");
HttpClient client = getConnection();
HttpUriRequest post = getRequestMethod(map, "http://cnivi.com.cn/login", "post");
HttpResponse response = client.execute(post);
if (response.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
String message = EntityUtils.toString(entity, "utf-8");
System.out.println(message);
} else {
System.out.println("請求失敗");
}
}
}
=============END=============
以上內容為轉載，只是把三個文章的內容整在了一起
---------------------
作者：單人_旅途
來源：CSDN
原文：https://blog.csdn.net/wjrong_1/article/details/51114233
版權聲明：本文為博主原創文章，轉載請附上博文鏈接！